# Tag Info

20

TL;DR: Virtually zero. The distances between stars are HUGE and stars are tiny compared to the astronomical scales of distance between neighboring stars. The sun, is about 0.0000001 or one ten-millionth of a light year. The probability of a star (to be generous, say a $10 R_\odot$ star) colliding with the Sun is tiny. Every star has a different velocity ...

10

As fasterthanlight says, the probability of our Sun colliding with another star in the galaxy is virtually nil. In fact, the probability of any star in the galaxy colliding with another (unrelated) star is very small. Stars can and do collide, but they're stars that are already gravitationally bound to each other in binary or multiple star systems. And they ...

9

Well the spin is easy. Your system has zero angular momentum, so the spin will be zero. I think there will also be no gravitational radiation. for the slightly technical reason that gravitational waves only come from changes to the quadrupole moment of a system and in your system the quadrupole moment is always zero. So everything ends up in the final ...

6

If you are talking specifically about our solar system, then no. There were many collisions during planetary formation, and there is the fairly well regarded theory that our moon was formed by a collision around 4.5 billion years ago (The Theia Impact, if you want to do more research) but aside from that, collisions aren't really possible any more, except ...

6

Fairly good. Two stars of mass $M$ falling from infinity straight towards each other until they merge at distance $2R$ will get kinetic energy $GM^2/R$. This is a lot, for two suns it is $1.8978\times 10^{41}$ J. However, compared to the binding energy of even a single star, $\approx 3GM^2/5R$ this is less(the sun has binding energy $2.2774\times 10^{41}$ J, ...

5

"All earth orbiting satellites should have the same velocity" is not true. Kepler's Laws merely state that an object in a circular orbit at a particular altitude must have a particular speed. Not all objects in orbit are in a circular orbit. Non-circular (elliptical) orbital paths can cross one another as the object's altitude varies. Also, speed ...

5

Moon Even though the Moon obviously isn't a planet, it's a good place to start as most of the observations of meteorites hitting other bodies has been focussed on the Moon. NASA runs the Meteoroid Environment Office which in part monitors lunar impacts. They state; The lunar impact rate is very uncertain because observations for objects in this mass range ...

5

Collisions between a rogue brown dwarf and any other star would be very rare because the space between them is so vast. I don't want to say it'd never happen, but it would be a rare event. It's much more common for two stars that are already in the same system to collide by spiraling into each other, usually by tidal decay. A collision with a brown ...

5

Greenwood et al suggest that Earth had a lot of its water (maybe upto 70%) before Theia, but I can't find anything definite saying that it was liquid, although several sites reporting on the Greenwood paper assume that Earth was cool enough to have an ocean. It almost certainly had a crust, though. And immediately after the impact it had a magma ocean for ...

5

The shape of the surface shown in the video is a depiction of the spacial curvature of the spacetime. (The relationship with time are depicted seperately by the arrows and the colors.) More particularly, the shape is depicting the curvature of equatorial plane of the binary. The depicted surface has been embedded in a (fictional) 3D space in such away that ...

4

The expansion is overridden on a small scale by gravity. Our galaxy is not expanding, and the stars are bound together. In fact, a whole group of galaxies don't notice the overall expansion.

4

... and still remain within the habitable zone? Everything perturbs all the time. Every change in the distribution of mass in the solar system (or in the universe) perturbs the orbit of the Earth... so the literal answer is "yes". But suppose someone asked instead: Can an 'invisible' impact perturb the orbit enough to have a measurable effect on ...

4

If the Sun collided with another star about the same mass, then its mass would be slightly less than 2 solar masses, as some material would be ejected away from the merger. This would result in an A-type star, as the merger's mass is about 2 solar masses. A good example of a 2 solar mass star is Fomalhaut A, which is an A3V star. Therefore, this merger ...

4

How much mass would have to be added to the Sun to significantly alter its characteristics Asking how much would be significant is inexact. The Sun is classified as a G2V main sequence star. Though the chart lists one solar mass as G4V, so there's some variation in there. The classifications seem to relate to temperature. To go 1 step up (and using ...

4

Imagine that that there are 2 pigeons on LSD flying around the world. What are the chances that they would collide? Colliding stars are less likely because if the stars were as big as pigeons, their average distance would be 200,000 kilometers. Stars travel at 500.000 mph on average, so if they were birds, the birds would be flying at 0.000005 mph. Stars are ...

3

According to Kepler laws all earth orbiting satellites should have the same velocity. This is not correct. It is not even close to correct. Mercury orbits the Sun at a much higher speed than does Pluto. Just as bad, you are conflating speed with velocity, which are two very different things. By way of analogy, consider the case of a person who mistakenly ...

3

The dynamics of the Solar System and the chemistry of the Solar System bodies don't support a hypothesis of a stellar merger later than formation of the protoplanetary disk which would have mixed-up things considerably and heavily disrupt any circumstellar disk. Thus this basically excludes any collision after the time one can start talking about a protostar,...

3

No. A short calculation: the Moon orbits the Earth with with 1022m/s. The mass of the Earth is 81 times bigger than of the Moon. That means, that also the Earth orbits the common center of mass of the Moon-Earth system by $\frac{1022}{81}=12 m/s$. The largest possible indirect effect of such a Moon impact would be roughly so high, as if the Moon would ...

2

The merger of two stars may only result in a supernova if the merging stars are white dwarfs, or possibly a white dwarf with a neutron star, and even in these scenarios a supernova is not certain. Other mergers do not cause supernovae. Examples are the formation of contact binaries (W UMa binaries), which may then fully merge to produce fast-rotating FK Com ...

2

Are there any scenarios in which two stars could collide, and simply fuse without triggering a supernova As said in the comments, binary evolution of stars is very uncertain, but there exist numerous codes (i.e. MESA, STARTRACK, BSE, etc...) which incorporate LOTS of physical processes over the course of millions of years (and if they evolve to black holes ...

2

Planetary Scientist Sarah Stewart's research is on the formation of the moon, not, as far as I can tell, as much on the chemical composition and precise temperature of the atmosphere after impact, so I don't know if plasma is all that relevant to her work, but I think she'd have to model and account for total energy and temperature, similar to what you did ...

2

Consider an initially stationary particle of matter and suppose a 1 Earth mass black hole flies past it at speed $v$ on a trajectory that passes the initial position of the particle at distance $r$. The particle will be mainly affected by the gravity during a time period of roughly $r/v$ (up to some "geometric" constants), during which time it will ...

1

Stellar mergers are certainly possible, but also relatively rare. Maybe protostars merging is a bit more common since they have less relative velocity. However, unless the merger is straight it will typically deposit a lot of angular momentum. The sun seems to be a slow rotator for its spectral class. Hence it is not likely it was formed through a stellar ...

1

All these objects are rocky, also the icy ones given the low temparatures at their usual orbits. Your observation is also correct, that mutual collisions at usual orbital velocities in today's solar system tend to be catastrophic among the remaining small objects (comets, asteroids, KBOs etc); that is even true when you consider that usual collision ...

1

In short: Not every gas is a plasma. Covalent bonds can be absent in a neutral gas. Rock vapour is just vapour, silicate atoms in their gasous state. And just as oxygen can freeze, so can silicates evaporate. Of course they can thermally ionize as well at even higher temperatures, but I don't see that this is implied in the text. They're not the only ones ...

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